1. Field of the Invention
The present invention relates to a storage device which is adapted to diagnose a writing unit, and writing unit diagnosing method.
2. Description of the Related Art
A magnetic disk device makes a write current, which is reversed according to data, flow through a write head (magnetic head) so as to record data to a medium. In recording data, in case a defect in property or degradation in connected resistor occurs in write parts such as a write drive circuit (preamplifier), a suspension, a write head, and connected portions of respective parts which are parts related to the write operation, suitable magnetization reversal cannot be formed on the medium. These defects in write parts are discovered at the time of the read operation, and not only an error rate but also may lose the data in the worst case.
Next, a method of checking the write operation in the conventional magnetic disk device will be explained.
As a first method, there is employed a method under which a preamplifier compares the voltage of a write head with a threshold to check whether or not the write head is defective (write head is OPEN or SHORT).
As a second method, there is employed a method under which the verifying (read) operation is performed after the write operation in accordance with a command from the user to a magnetic disk device to assure the write operation.
As a conventional technique related to the present invention, there is known a magnetic disk memory device that detects whether or not a write head is OPEN or SHORT. (for example, refer to Patent Document 1: Jpn. Pat. Appln. Laid-Open Publication No. 2002-269707)
However, in the above-described first method, the threshold value is uniform with respect to all the heads in a magnetic disk device. Accordingly, only a case in which a write head becomes defective (write head is OPEN or SHORT) can be notified. Similarly, also in the above-described second method, only a case in which the write operation cannot be performed after the write operation can be notified. Therefore, there have been some cases in which written data cannot be restored.
As described above, since it is determined that a write head is defective after the write head has become defective, there have been some cases in which the system is suspended or the restoration of the system becomes difficult. Furthermore, in recent years, it becomes a significantly important task to suppress the suspension of the system due to breakdowns of components of the system and so on to the utmost extent.